12.5. Questions and Tasks
249
rel_dens3 = if total_wt3 and Biomass_1029 >0 then
total_wt3 /Biomass_1029 else 0 {unitless}
total_wt3 = ave_wt_3*Urchin_1115 {kg}
tto3 = 9 {month}
Urchins 1620
Dead4(t) = Dead4(t-dt) + (die4) * dt
INIT Dead4 = 0 {urchin}
INFLOWS :
die4 = (Urchins_1620*nat_death_rate) + number1620eaten
{urchin/month}
Urchins_1620(t) = Urchins_1620(t-dt) + (to_1620-die4to_2125) * dt
INIT Urchins_1620 = 1750000 {urchin}
INFLOWS :
to_1620
OUTFLOWS :
(IN SECTOR : Urchins 1115)
die4 = (Urchins_1620*nat_death_rate) + number1620eaten
{urchin /month}
to_2125 = (Urchins_1620 -die4) /tto4 {urchin /month}
ave_wt4 = 0 .00272 {kg /urchin}
Biomass_30plus = total_wt7 + total_wt8 + total_wt9 +
total_wt10 + total_wt11 + total_wt12 + total_wt13
kg1620eaten = if Biomass_30plus > = Kg_Urchin_consumed
then rel_dens4*Kg_Urchin_consumed else total_wt4 {kg}
number1620eaten = kg1620eaten/ave_wt4 {urchin}
rel_dens4 = if total_wt4 and Biomass_30plus >0 then
(total_wt4 /Biomass_30plus) else 0 {kilogram per
kilogram per time}
total_wt4 = ave_wt4*Urchins_1620 {kg}
tto4 = 9 {month}
Urchins 2125
dead5(t) = dead5(t-dt) + (die5) * dt
INIT dead5 = 0 {urchins}
INFLOWS :
die5 = (Urchins_2125*nat_death_rate) +number2125eaten
{urchin/month}
Urchins_2125(t) = Urchins_2125 (t-dt) + (to_2125-die5to_2630) * dt